Nerve Conduction Velocity (NCV)

Nerve conduction velocity is a test of the speed of electrical signals through a nerve. A nerve conduction velocity test is usually performed along with an EMG.

How the Test is Performed

Patches called surface electrodes, similar to those used for ECG, are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve. The nerve's resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to determine the speed of the nerve signals.

How to Prepare for the Test

Normal body temperature must be maintained (low body temperature slows nerve conduction). Tell your doctor if you have a cardiac defibrillator or pacemaker, as precautions may need to be taken.

How the Test Will Feel

The impulse may feel like an electric shock. Depending on how strong the stimulus is, you will feel it to varying degrees, and it may be uncomfortable. You should feel no pain once the test is finished.

Often, the nerve conduction test is followed by electromyography (EMG), which involves needles being placed into the muscle and you contracting that muscle. This can be uncomfortable during the test, and you may have muscle soreness after the test at the site of the needles.

Why the Test is Performed

This test is used to diagnose nerve damage or destruction. Occasionally, the test may be used to evaluate diseases of nerve or muscle, including myopathy, Lambert-Eaton syndrome, or myasthenia gravis.

Risks

There are no risks.

Considerations

An NCV test shows the condition of the best surviving nerve fibers, so in some cases the results may be normal even if there is nerve damage.